Railway signaling system



061C. 26, 1943. C, E STAPLES ETAL 2,332,874.

RAILWAY SIGNALINGV SYSTEM Filed Jan. 28, 1943 a, z WM@ u IHEI/Q ATTORNEY not interfere with In the drawing Fig.` i` is Patented ct.2'6, 1943 T OAFFICE t l RAILWAY SIGNALING sYsTEM e Crawford E. Staples` and Herman G. Blosser,

Pittsburgh, Pa., assignors to The Union Switch & Signal-Company, Swissvale, Pa.,a corporation" of Pennsylvania y Y ApplicatonJanual-y 28, 1943, Serial No. 473,792

solaires. (c1. 246-38) ous signaling `functions without the use of line wires. l

It is an object of our invention to provide improved apparatus of the type described which employsi a feed-back detector relay of the stick polar type, and which is arranged so that -the alternating current cab signal control energy is supplied to the section rails vover acircuit independent ofthe feed-back relay.

master code. to the railsk of a track section will operation of the feed-back detector relay. 1

` A further object of theinvention is toprovidey improved apparatus of the typeldescribed which includes means for delaying response of the feedback detector relay to energy ,supplied thereto from alocal source to thereby-substantially equal- .Another object of the invention is to provide improved apparatus of the type described which `is Larranged so that Venergy `stored in "the track Y ballast as a result of the supply of-impulses of izesthe periodsiin whichthe contact of this relay is-in its normaland its reverse positions.

Other objects ofthe invention and features of novelty will be apparentlifrom the followingde- `scription `taken in connection `with the accompanying drawing.

Y We' shall describe one form of railway signalploy, and shall then point out the novel features thereofin claims. 1 l

a `diagram of a section of railway track equipped with track circuit apparatus embodying our invention, and r Fig. 2 is a fragmentary diagram showing a modiiication which, we may employ.

`Similar reference characters refer to similar parts ineach ofthe two views.

In practicing our invention we provide the feed-back detector relay, with two windings. A ,corfrtact` of the associated coding relay, when released, connects one of thesev windingsA across the sefctionfrails, While the impulse of feed-back enegy supplied over the` section rails to this" winding causes the relay contact `tobe movedto one of its positions. When the coding relay contacts are picked up.,` the track battery and track transpforrner are connected across the section rails independently of the feedfback relay track wind-A ngwhle al.,co'ritacit ofthe-coding relay` establishes a circuit to supplyenergy from a local source of direct current to the other winding of `the feed-back detector ,relay and .thus cause the l relay contact tobe moved to its other' position.

Referring to Fig. 1 of the drawing,there is shown therein a section of railway track'having track rails I and 2 over which traffic` normally moves in the direction indicated by the arrow, that is, from left to right. The track rails of each` section are separated from the rails of the adjoining sections by insulated joints 3 in the usual manner.l f l `The equipment at the entrance end of thetrack section may be arranged in any. manner well known in the art, but itis preferred to arrange thisy apparatus in the manner shown in Letters Patent of the United States No. 2,286,002, granted to Frank H. Nicholson on June 9, 1942.

The equipment at the entrance end ofthe track section `includes a track relay TR, a decoding transformerDT, .an impulserelay IR, an auxiliary relay H, anda battery FB. `The track relay TR. is of a type the contacts of which when released become picked up on the supply of energy trol a signal, not shown, at the entrance to the s section.

This invention isconcerned with the arrangement of the equipment at the` exit end of the track section. .This equipment includes a feedback detector relay K, an approach relay AR, a coding relay CR, aftrack `transformer TT, and atrack battery TB. i.

. The detectorrelay K is of .the stick polar type and its contact when moved to either of its two positions will remain in :that Vposition `until a winding of the relay is supplied with'energy effec'- tive to 4move the relaycontact toits other` posi- The coding relay'CR is provided with contacts which are continuously picked up and released at one `or another of a plurality of different rates depending ontrafiic conditionsin advance. lOne means for controlling the .relay 'CR isashown in Fig. 5 of Letters Patent/of `the United States No.A

2,174,255 granted to Herman GgBlosse/r.

The `approachrelay' AR controls' the supplyof energy to the track transformer' TT from -`a suitable source of alternating current, not shown, the terminals of which are designatedBX and CX. Therelay AR may also be lemployed"tobontrol lighting of a signal, not shown, for the adjacent section in advance.

The equipment at each end of the track section includes a suitable source of direct current, not shown, the terminals of which are designated B and C.

The equipment is shown in thel condition which it assumes when the-l track section is vacant. When Acontact l vof coding relay CR is in its picked-up position, it interruptsthe circuit of the track winding II of relay K, and connects thev track battery TB across the section lrails in series f with the secondary windingof the track transformer TT and the current limiting resistor I2. The track battery is connected with the section battery FB to the track Winding II of relay K over the section rails. This circuit is traced from the positive terminal of the battery FB over front contact I4 of relay IR, through the winding of the track relay TR from its right-hand to its leithand terminal, over track rail I, through track winding II of relay K from its left-hand to its right-hand terminal, over back contact IE! of relay CR, track rail 2, and resistor 28 to the negative terminal of the battery FB. The energy supplied through the track relay winding flows through the winding in the wrong direction to pick up the relay contacts so they remain released at this i time. Y

rails in such manner that the positiveter'minal of the battery is connected to' track rail II. As

the section is assumed to be vacant, master code energy from the track battery flows from the positive terminal of Vthe battery over rail I through the track=r,elay winding from its lefthand to its right-hand terminahover back con- Atact I4 of relay TR, track rail 2, front contact Iii ofA relay C R, resistance I2, and-track transformer secondary winding to the negative terininalacf the battery. L. n 1

The energy from the track battery owing through the winding of the'track relay TR causes the contacts of the relay to pick up. `On picking up of the track relay contacts .there is' a change in, energization of the. primary lwinding off the decoding transformer, and energyyis induced in the transformer ,secondary windings.. Energy from one of these windings isy rectified byV a contact of the track relay and is` supplied to the relay I-I. Energy induced in the other secondary winding of the decoding transformeris supplied to the impulse relay IR. The relayIR, however,

. is of a type thecontacts of which become, picked continuato "connect the .tra'ck'relay across 4vthe section rails.

In additioncn picking up of the contacts'of relay CR, its contact I5 establishes the circuit to supply energy from ailocal source .to thelocal Winding I6 of relay K. `This energyfflows through the winding I5 in the direction effective to move the Contact I8 of the yrelay to its right-hand or reverse position in which it interrupts .the circuit of the relay AR.'A 'f 1 On release of the contacts of relay CR contact I5 interrupts the circuit of winding It of relay K, while contact Illinterrupts the circuit ofthe track battery and connects the track winding I I of the relay K across -the section rails.

When the circuit of the track battery is interrupted, the contactsof thetrack relay'TRI release and there is a change-in energization in the primary windingwof'the decoding transformer so thatan impulse of ,energy is induced in each of the transformer secondary windings and yis sup- The energy supplied from the battery FB to the track winding kI I of relay K causes the contact I8 of the relay to move to its left-hand or normal position in which it establishes the circuit of the relay AR.

The impulse of energy supplied from the decoding Jtransformer DT to vrelay IR is eective to maintain` the'relay contacts picked up for only a short period so the contactllireleases and cuts olf the supply of energy from the battery FBto the relay K and connects thel track relay TR across the section rails, and the equipment is then in the condition shown in Fig. 1 of the drawing. `Before the relay IR releases, however, the ,contact I8 lof relaYK will have been moved to its normal position, and, because of the operating characteristics ofthe relay, will remain in that position after the supply of energy to Winding I I is cut off. Y,

During subsequent `picked-'up periodsY of the coding relay CR the trackA batteryis connected across the 'section rails, while energyis supplied to the local winding I6 of the relay K so that itscontact It is movedvto its reverse position. During subsequent released periods of the relay CR the track winding Il of relay K is connected across the section rails sothat impulses of yfeedback energy supplied over the Vvsection rails may feed to theV winding II of relay. K and move the relay contact I 8 to its normal position.

As longfas the'secti'on: is vacant, therefore, the contactl of' relay Ki is moved to its f normal position to establish the ycircuitof relay AR during each /releasedperiodlof thecontacts of relay CR.'` The circuit of. relay `ARis interrupted during each 'picked-up period of'A the contacts of relay CR, but the relay AR is of a` type the contacts'of which are slow` enough in releasing to remain pickedup during the picked-up periods of therelay CR.

Accordingly, as long as the section is Vacant, contact 2l of relay AR is picked upiand cuts off the supply of energy to th'e'primary winding of the track transformer TT, while 'it shunts this winding toreducethe impedance of the transformer secondary winding.

When .a train enters the section-,fthe track relay remain's released andr energyvisnovlonger supplied through the decoding-transformer D'I to the relays H and .IR so that their 'contacts remain released, andr relayA IR "does not establish the vcircuit to supply' impulses of 4feed-back energy from the batterynrto the sectionrails. Furthermore, the train shunts' the Vsection rails, andthe supply of feed-back energystorelay cutoff. Accordingly, during each Apicked-,up period ofthe contacts of relay CR. 'eri4e1"'gy`I` is supplied to the localjwinding I6`of relay.K ar'icl'uthe relay con-V tact 'I8 is nicved 1to1' its ,right-lgiand or reverse each released period ofthe contacts ofV relay'CR supplied to the section rails.

assasm thetrack winding n of 4relay vK is ccmiect'ei` lay `ARl The contact 2l of relay ARftherefore, y

releases and* establishes the circuit forsupplying energy tothe primary Winding 'of track trans-` former TT so that during the picked-up periods ofrelay CR energy is supplied to the section rails from the. track transformer as well as from the track battery. Theenergy'` supplied "from the track transformer tothe section' rails may con'- trol theY cab signalsapparatus cnthe locomotive oftheltrain in the track section.

When the train passes out of the section, the impulses of `master code supplied.l from the battery TB to the section rails feed to the `track relay vand operate it so that the impulse Arelay IR, causes impulses .of feed-ba`ck energyto be The impulses of feed-back energy feed to the track winding II of relay K over back Contact I of relay CR, andcause contact I8` of relay K to moveto its left-hand or` normal position andiestablish the circuit of relay AR so that its contact 2| picks up and cutsoif the supply of energy to transformerTT. l

,In addition; as a result of the supply` of master f code to the track relay, energy is Supplied relay H and l section rails Will not fcauseeimproper operation of the relay K. As explained above, when the contacts` of relay CR are picked up, the track battery TB is connected across the section rails, while energyis supplied to the local Winding I6 ofyrelay K to move contact I8 to its reverse position in which it interrupts the circuit of relay-AR: On release of the contacts of -relay CR, thesupply-of energy from the track battery `TB toA the ysection rails is cutoff, While conta'ctI connects the track `Winding II of relay K across the section rails and contact I interrupts the `circuit uitvinding I6; l

l If at this 'time the section is occupied, impulses of feed-back energy will not be supplied overthesection rails -to the track Winding II of relayK, 'but' energy stored in the track circuit as a result of the supply of master code to the section rails Willofeed to the winding `I I. When coding relay Contact IIJ is picked up the `battery f TB isconnectedaacross the section railsWith the positive terminal of the battery connected to trackirail l. On release of contact :i0 the supply of energy from the track battery uto the section rails -is cutoff, but'because of the inductance of the track circuit. energy-will continue `to flowy therein in the same direction in which it had been flowing: Accordingly, energy will now from rail I xto'raili 2 through `the wheels and 'axles olf" tlfi'etrainfin` the section, overfback contact I 0- ofrelayCR, and through windingV II of relay K frornrightV toileft to rail I. The direction of iloivvrof this energy through the winding `II Vis such that it noidscontact la Ofreiay `is iii-its reverse position in Whichfit interrupts lthe circuit of relaytARjfV i .When the apparatus is arranged asshoWn -in Fig: 1,:th'eicontact of `relay K will occupyitsre`A verse position 'for somewhat longer period'sfthan it is in' its normal position. This may be objec` tionable and in Fig. 2y we have shownlinean's `for causing the periods in which the contact' ofrelay K occupies each. `of substantially equal. v-

The vfor suppi'ying'energy tothe coding relay CR is arranged so that the picked-up and released periods `of the contacts of the relay CR are substantially equal in length. lOn picking up of the contacts of'relay CR `contact I5 establishes the vcircuit of winding lr6 of relay K;y and when the equipment is arranged as `shovvn inlig. l, the-contact I8 of relayK responds almost Ain'- stantaneously 'and moves to its reverse-position.

` i Ori release of the' relay CR, contactl` interrupts `the circuit of the track battery and con-l nects ythe winding II of relay -K across the seotion rails, While contact I5 of relay CR` interrupts the circuit of relay K. Oninterruption of the circuit of the track battery the trackrrelay releasesand` causes an impulse of energy tobe supplied from the decoding 'transformer DT'to relay IR so that the contact rIIloi" relay IR-picks up and establishes thefcircuit 4for supplying energy from `battery FB over thesection railsitol l the Winding VII of relay K. l i

` Accordingly,` there is a time interval from'lthe instant of release of the contacts of relayCR until energy Ais suplied overthe track rails torelay K; theV lengthfof thisv time interval being dei termined by the release timeof relay TR and the pickup" time of i relay IR, Whileik a further short timeelapses before4 the relaynK responds to energy supplied over the section `rails.

Since the contact-0 1` relay K responds almost instantaneously on pick-up of relay CR,an'ol` as there is some delay in the response of the `contact ofrel'ay K on releasing of relay CR, the contact-of` relay K will be in its reverse position for somewhat longer periods" than it is -in itsr` normal position. `In the modification shown inFig.` 2 means is provided for;` delaying responserof-relay K tolenergysup'plied to Winding I 6 0n pick-up o1 relay CRvfor substantially` as long asis required for relay K to respond `to energy supplied over the trackrails to thereby equalize the periods during which the contact of relay K occupies each of its two positions. y Y

In the modification shown in Fig, 2 an impedance in the form of a reactor 24 is connected in series with the circuit'of Winding IS-of relay K, While a condenser 25 is connected inVVK multiple Withkthe reactor 24.. The apparatus of Fig. 2 is otherwise thesame as that shown in Fig. 1.

When thecontacts ofV `relay CR pick up,`-con tact I5 establishes the circuit for supplying energy to winding iii ofrelayK in series With reactor` 24 and condenser `25.

actor buildsfup, vvhile initial ,flovv of energy through `the winding of the reactor and also through theV Winding I6 of relay K is delayed While a charge is built upon the condenser 25.v

Afterthe core of the reactor ilssaturated, energy flows freely through the winding ofthe Areactor to the windingv I6 of relay K, While the energy stored inthe' condenser is discharged byow of its two positions# to be Flow of energy through the reactor 2J to Winding I6 of relay K is retardeduntil the fluxin the core v'of the reresponse of relay K to energysupplied over -the Sectionl rails. A I t, j .Y .y

When vthe,contacts of relay CR release' contact I5 interrupts` the circuitr of the v reactor 24 and of the winding I6 of relay K, and theux in the core of; the reactor 24v collapses, thereby inducing in the winding of the reactor an impulse of energy reactor winding onopening of contact I5 flows K vthrough winding I6 of relay K and is dissipated in the arc which forms on opening oftcontact I5.

Astftl'ie condenser 25 absorbs a substantial part of the v ,energyrv induced lin the `reactor windingV the arc-which occurson opening of contact I5v is much smaller thanv would be present if the c ondenser wereV not provided, and the life of the contacts Ais `correspondingly increased.

,Iherenergy supplied from the reactor 24 t0 the Winding i6 of relay K is of such polarity that it holds the contact I8 yof relay K in the position rwhich it already occupies, that is, its reverse, position, whileV the impulse of energy supplied from .the reactor to Vthe-winding I6 of relay K is of such short duration,that the impulse terminates before energy supplied over the` sectionrails reaches winding I I of1 relay K. Accordingly, the

impulse of energy supplied from the `reactor to the winding I6 of relay K does notl interferewith or Adelay response of relay K to energy supplied over ,the section rails. g f

As the modification shownv in Fig. 2 includes means effective on picking up of the contacts of relay CR for delayingv response of relay K'for a .periodg'substantially equal to the period that response of relay K is delayed on release of the contactsof` relay CR, the Contact of relay K will occupy each of its two positions substantially one-,half of the time, and the circuit or circuits controlled by the contact of relay K will be complete a sufficient proportion of the time to insure proper operation of the equipment energized over such circuit or circuits. ,y

Although a reactor is shown in the circuit of the winding I5 of relay K, the invention is not limitedfto the use of an impedance of this type, andan impedance of another form may be'employed, as for example, a resistor which restricts the flow of energy to the `relay winding and thus Vdelays,.building up of flux in theA relay core to thereby delay response of the relay.

While the inventionl hasbeen illustrated and described in connection withtrack circuits in which coded alternating current cab signal control energy is suppliedA at times to the track rails, the invention is not limited to use in such situations, but is equally applicable to track sections to which only coded direct current is s upplied, y

Although we have herein shown and described only Aone kform of railway signaling apparatus embodying our invention, together with a modicationwhichwe may employ, it is understood thatvarious changes and modications may be made therein within the scopeofthe appended claims without departing fromY thev spirit and scopeiof. ourl invention.' e

Having thus described our invention, whatwe claimisp. Y f v ,t v 1,., In a codedfrailway signaling system,y in combinatiom a1 section of railway track through which traiiic normally moves inone direction,

`anode following `trackrelay at the entrance end ',of said. section energized -byV current supplied over the Vrails of said section, a polarized code .following,detector` relay located atvthe exit end of-the section -and having a track winding and a local winding, a coding device having contacts .continuously actuated between a first and a second position, a contact of said coding device being effective when in its first position to connect ,the track winding of saiddetector relay across the section rails and being elective when in its secondgpositionto connect a track battery across the section rails,'another contact of said coding device 'being eiiective` when in itsrsecond positionto establish a circuit to supply tothe local winding of said detector relay energy eective to cause the contact of said detector relay to be moved to its reverse position, means operative on release, of the track relay contacts to supply to the track rails an impulse of energy of a ,polarity which when supplied to the track winding of the' detector relay causes the contact of said detector relay Yto be moved to its normal -position, and an approach relay governed by said detector relay contact, Y

2. In a coded railway signaling system, in combination, a section of railway track through which traftlc normally moves in one direction, a

Vcode followingY track relay atlthe entrance end of said section energized by current supplied over the rails of said section,` a polarized code following detector relay located at the exit end of the section and having a track winding anda local winding, avcoding device having contacts continuously actuated `between a-rst and a second position, a contact of said coding device being eiiective when in its i-lrst position to connect the track winding of said detector relay across the section rails and being effective when `in its second position to connect a track battery and the secondary winding of a track trans- `relay contacts to supply to the track rails an impulse of energy of a polarity which when supplied to the detector relay track winding causes the contact of said'detector relay to be moved toits normal position, and an approach relay governed by said detector relay contact.

`3. In a coded railway signaling system, in combination, a section 'of railway track through which ltraiiic normally moves in one direction, a-code following track relay at the entrance end of said section energized byy current supplied over the rails of said section, a polarized codeV following detector relay located at the exit end of the section and having a track winding and a local winding; a coding device having contactsv continuously actuated between arst and a second position, a contact 'of saidlcoding device being A 2,332,874 r to the local winding for said detector.` relay energy? effective to cause `the."contact oisaid detector `relay to belmoved toits reverse'positioni means operative on release ortho ltrack relay `contacts to supply to the track'rails an impulse ofllenergy of a polarity which when suppliedto-the detector relay `track*wirding causesthecontactpi Vsaid detector relay tobe moved to itsnormal position,

and an approach relay governed by said detector i relay Contact' and y'controlling the supply of "energy tothe primary winding of saidtrack transformer".v

and a second track` rail `over which traflic nor-V mallyf moves in'-` one direction, a code following track'wrelay at the jentrance end of` saidsection energized `by current suppliedover vthe section raiisfa polarized code following` `detectorrelay located'atthe exit endof the section an'dhaving a contact whichismoved to its `normal Aor its reverseVL position according' as `energy flows through'a winding or the-relay!! from its first to itssecond terminali'or froniits second-its first terminal, acoding device `havingcontacts oontinuonsiyiactnateo between a' first anda seo`` bination, asection of railway"`tack having fau first track rail, afcodingdevice having contacts continuously actuatedbetween aiirst and "a seco'ndposition, a" contact of said coding `device be-v ing eiiective `according `as it` is in itsrst or its second position to connect said second track rail to the other terminal of said detector relay winding or to the other terminal of said track battery, another contact of said coding device being effective when in its second position to supply to a winding of said detector relay energy effective to cause the contact of said detector relay to be moved to its reverse position, means operative on release of the track relay contacts to supply to the -track rails an impulse of energy of a `polarity which when supplied to the detector relay is elective to move the contact of saiddetector relay to its normal position, and an approach relay governed by said detector relay contact.

5. In a coded railway Vsignaling system, in combination, a sectionof railway track having a rst and a second track rail over which traflic normally `moves in one direction, a ycode following trackrelay at the entrance end "of said'section energized by currentsupplied over the section rails, a polarized code following detector relay located at the exit end of the section and having a winding having one of its terminals connected to said i'lrst track rail, supply means comprising a track battery and a Vtrack transformer connected in series, one terminal of said supply coding device having contacts continuously actuated between a rst and a second position, a contact of said coding device being effective according as itis in its first or its second position to connect said second track rail to the other terminal of said detector relay winding or to the other terminal of said supply means, another contactof said coding device being effective when in its second position to supply to a winding of said detector relay energy effective to cause the contact of said detector relay to be moved to its reverse position, means operative on release `of the track relay contacts to supply to the track rails` an impulse of energy of a polarity which when supplied to the detector relay is effective to move the contact of said detector relay in its normal position, and an approach relay governed by said detector relay contact and controlling the supply of energy to said track transformer.

6. In a coded railway signaling system, in combination, a section of railway track having a first ono position, a vtrackfioattory, ajoonta'o't lorysaid codirigfdevice being effective`when `in lits `first" positicnto connect'tnetrack'pbattery through a ciruit'independent of said detector relay across the sectionrailswith the positive terminal ofthe batteryconnectdto said `iirsttrack rail,` acontact or Said coding-device boing effective 'when in its 'second .positionl `to connect sani'I detectori relay winding acrossthe section 'rails with the rlrst terminal; of' said iwindinw'g connected toi said firstct'rar'k"rail, a contact of saidfcoding relay being effective `when in its `iirst position tosupply to a winding dfsaiddetectorelay energy ei'ec reverse `positi across the section rails with the positive terminal of said source connected to said first track rail, and an approach relay governed by said detector relay contact.

7. In a coded railway signaling system, in

located at the exit end of the section and havi ing one of its terminals connected to said rst track rail, means operative on release of the track relay contacts to supply to the track rails an impulse of energy of a polarity which when supplied to the detector relay is effective to move the contact of said detector relay to its normal r position, a track battery having one of its terminals connected to said first track rail, a coding device having contacts continuously actuated between a first and a second position, a contact of l said coding device being effective accordingas it is in its first or its second position to connect said ,g Vsecond track rail to the other terminal of said means being connected to said iirst track rail, a v

550i, said track battery, another contact of said coding devicewhen in its second position estabdetector relay winding or tothe other terminal lishing a circuit for supplying to a Winding of said detector relay energy of `a polarity effective to move the relay contact to its reverse position, said circuit having an impedance associated therewith which delays response of said detector relay to energy supplied over said circuit for a period substantially equal to the period from Y l Y 4 means eifectiveon release'ofthe track relay contacts tofcoimect a 'source of energy'v lay( located at .theexit end of the sectionymeans operative; Qn releaseof *the trackA relay contacts to supply jto the track "rails'an impulse ofenergy Ofapolarity which When; Supplied to the detector relayi is effective tomove the contact of the-detectorreiay; to 4its normalposition, a coding vdevice"` having contacts continuouslyiiactuated between aaflrst and-a ;second position, a contact of said codingidevicebeinggeffectiye when in its second position Vtoestablish a\circuitto supply to a winding1.o fsaid detector relay energy eiective to move the ,contactgof said drelay to itsV reverse position, another contact of said coding vdevice being effective whenl in its second yposition kto connect a track batterygacross the section rails through a circuit-'independent :of Ythe .winding of said detectorrelay, a contact of said :coding device being effective ,when in its first position to con-v nect afwinding ofsaiddetectorjrelay across the vsection rails, and anapproach relaygovern'ed by said detector relay contact.- f s f l 9. In a coded railway signaling system, in com-'- binatiorna section .of vrailway track having a first and a secondytrackrailover which traic normally movesin one.,direction,a code following tracl'relaywatY the entrance end of said track section energized by current supplied over the section rails, a; polarized codenfollowing detector relay located 'at the exit'. end Voftlie s'ection,l means operative on release` of the track relayA contacts to, supply tothe tracks rails an impulse of energypf a polarity'which when supplied to the detector relay is effective to move the `contact of the detector relay toits normal position, av coding device-having contacts continuously actuated between/4a rst and a second position, aY contactof said coding -device being effective Whenin its second position to establish a circuit to supply to a YWindingof said ldetector relay energy eifectiveytomovethe contact of said relay to its reverse position; said `circuit having asso-A ciated therewith- Vmeansrfor` delaying response ofsaid detectorl relay to energy supplied over said circuit for a predeterminedperiod*subse-4 and an4 approach relay governed by saiddetector relay contact..` t c Y ,i

' v CRAWFORD E. STAPLES.

HERMAN Ga BLOSSER1 

